I was reading about bleedless-787 power system but found out it still requires a gearbox.
What if you put coils around the "tube" part of the jet and tiny magnets in the end of the fan/compressor blades, this would generate an electric current that could be useful for powering the aircraft's electrical systems. With the right control system, it could perhaps also be used for precise corrections for vibrations/rpms resulting in better reliability and higher efficiency. Finally, it might be useful to assist the startup process by spinning the blades from 0 to some initial speed (ideally, replacing the starter mechanism but thats probably a stretch).
I know jet blades are subject to extreme mechanical and thermal stresses, so implanting a ferromagnet is probably not possible. But given the tremendous angular velocities, it probably doesn't require much magnetic material to induce a useful current. Perhaps a chemical spray deposition would suffice.
Has such a system been considered before? Are there any other obvious reasons this wouldn't work? Obviously there's no free lunch, and this system would steal angular momentum from the fan blades and require more fuel. But if it could somehow replace the generator and/or starter, it would yield tremendous weight savings.